Prognostic factors in patients hospitalized with pneumonia was analysed from 526 non-immunocompromised host patients who were admitted to the Medical Department of Chulalongkorn Hospital during the period of January 1987 to December 1991. The overall mortality was 30.5 per cent. The causes of death were 12.7 per cent of progressive or uncontrolled pneumonia, 10.1 per cent of underlying diseases and 7.2 per cent of complications of assisted ventilation. Patients aged 60 or older than 60 years, abnormal host, mental status changes, respiratory failure, shock, bronchopneumonia, g-ve pneumonia had significantly higher mortality than those who had no such conditions. Patients with pneumonia who had respiratory failure and shock had highest mortality at 70.2 and 85.1 per cent, respectively. Our study indicated that the presence of pleuritic chest pain and pleural effusion had a favourable effect on the outcome.